This invention relates to novel, highly efficient processes for the preparation of N-halogenated amides or imides such as N-halogenated hydantoins, succinamides, succinimides, phthatamides, phthalimides, cyanuric acid, glycolurils, and the like. Preferred aspects of this invention relate to novel, highly efficient processes for the preparation of 1,3-dihalo-5,5-dimethylhydantoins. As used herein, such terms as halogen, halogenated, and halo refer to bromine and/or chlorine.
Various N-halogenated amides and imides are of known utility as chemical intermediates, as halogenating agents in organic syntheses, and as biocidal agents. See for example, U.S. Pat. Nos. 2,868,787; 2,920,997; and 2,971,959.
1,3-Dihalo-5,5-dialkylhydantoins, especially 1,3-dibromo-5,5 limethylhydantoin, 1,3-dichloro-5,5-dimethylhydantoin, 1 -bromo-3-chloro-5,5-dimethylhydantoin, and 1 -chloro-3-bromo-5,5-dimethylhydantoin, or mixtures of two or more of them, are biocidal agents for use in water treatment. These compounds are, in general, sparingly soluble in water. Each of these compounds except 1,3-dibromo-5,5-dimethylhydantoin, has been supplied in compacted solid forms such as granules, tablets, or briquettes, and delivered into the water being treated by means of water flow through an erosion feeder. So far as is known, 1,3-dibromo-5,5-dimethylhydantoin powder has not been converted into a compacted form for such use.
Over the years considerable effort has been devoted to the search for improved methods for producing N-halogenated amides or imides. In U.S. Pat. No. 2,971,960 N-brominated compounds such as N-brominated 5,5-di-lower-alkyl hydantoins are formed by treating the alkylhydantoin with bromine in an acidic aqueous solution containing hypochlorite, preferably at a pH between 1 and 4. However, the method of choice has been halogenation of the alkylhydantoin in a basic aqueous medium. Almost invariably the halogen has been introduced into, or formed in situ in, the aqueous medium containing the alkylhydantoin. See in this connection U.S. Pat. Nos. 2,398,598; 2,779,764; 2,868,787; 2,920,997; 2,971,959; 3,121,715; 3,147,259; 4,532,330; 4,560,766; 4,654,424; 4,677,130; 4,745,189; WO 97/43264, published 20 Nov. 1997; Orazi and Meseri, Anales Assoc. Quim. Argentina, 1949,37, 192-196; Orazi and Meseri, Anales Assoc. Quim. Argentina, 1950, 38, 5-11; Corral and Orazi, J. Org. Chem., 1963, 23, 1100-1104; Jolles, Bromine and its Compounds, Ernest Benn, London, 1966, p. 365; and Markish and Arrad, Ind. Eng. Chem. Res., 1995, 34, 2125-2127.
Shortcomings of prior processes for the N-halogenation of amides and imides include the requirement for careful temperature control (particularly in order to avoid sudden exotherms), long reaction times, foaming due to evolution of gases from decomposition of reactants and/or reaction products, and products of inconsistent quality.
In the case of 1,3-dihalo-5,5-dimethylhydantoins, the provision of a process capable of producing the product as relatively large particles is a desirable objective. U.S. Pat. No. 4,745,189 refers to formation of N,Nxe2x80x2-bromochloro-5,5-dimethylhydantoin products comprising relatively large particles. Unfortunately, however, the process requires halogenation of dimethylhydantoin in an aqueous mixture under alkaline conditions in the presence of a halogenated alicyclic organic compound such as dichloromethane.
It would be of considerable advantage if a new way could be found of producing N-halogenated amides or imides while avoiding or at least minimizing the extent of the shortcomings referred to above. It would also be of great advantage if a way could be found of producing 1,3-dihalo-5,5-dimethylhydantoins having larger average particle size than produced by methods known heretofore. Also it would be of considerable advantage if the production of a larger average particle size product could be accomplished without need for use of a halogenated organic solvent in the reaction mixture.
This invention is deemed to fulfill these objectives in a most effective and efficient manner.
In accordance with this invention processes are provided which are characterized by high efficiency, uniform product consistency, good product color, and efficient utilization of reactants. In addition, this invention makes possible the conduct of exothermic N-halogenation reactions without use of costly refrigeration. Moreover, the processes of this invention can be run in a batch mode, in a semi-batch mode, or in a continuous mode, and in any such mode it is possible, when producing products devoid of chromophoric groups, to obtain high yields of very pale yellow to almost pure white products. And no haloorganic solvent or co-solvent of any kind is required in the processes of this invention.
Furthermore, this invention makes possible the production of 1,3dihalo-5,5-dimethylhydantoins with large average particle sizes without use of any halogenated solvent or co-solvent in the process. For example, 1,3-dibromo-5,5-dimethylhydantoin with an average particle size of at least 175 microns can now be readily formed pursuant to this invention. In fact, 1,3-dibromo-5,5-dimethylhydantoin, with an average particle size of over 300 microns has been produced using a process of this invention. As will be seen hereinafter, measurements carried out on samples of several commercially-available 1,3-dibromo-5,5-dimethylhydantoins obtained from different commercial sources showed that the largest average particle size of these commercial products was only about 162 microns.
One of the embodiments of this invention is a process for the N-halogenation of a compound having in the molecule at least one halogenatable amido or imido nitrogen atom. The process comprises concurrently, or substantially concurrently, feeding (a) a compound having in the molecule at least one N-halogenatable amido or imido nitrogen atom, (b) an inorganic base, (c) a brominating agent and/or a chlorinating agent, and (d) water, where (a), (b), (c), and (d) are fed individually and/or in any combination(s) whereby the feeds come together in a reaction zone. In addition, (a), (b), (c), and (d) are fed in proportions such that at least one such amido or imido nitrogen atom is substituted by a bromine or chlorine atom, thereby forming product which precipitates in an aqueous reaction mixture, and such that the pH of the aqueous reaction mixture is continuously or substantially continuously maintained in the range of about 5.5 to about 8.5 during all or substantially all of the time such feeding is occurring.
Another embodiment involving the N-halogenation of a compound having in the molecule at least one halogenatable amido or imido functional group is a another concurrent feeding process. In this case, there are at least two separate but concurrent or substantially concurrent feeds to a reactor. One such feed is a brominating agent or a chlorinating agent. One or more other separate feeds deliver to the reactor a compound having in the molecule at least one N-halogenatable amido or imido nitrogen atom, an inorganic base, and water. A preferred process of this embodiment comprises concurrently feeding into in a reaction zone:
A) separate feeds of (i) an aqueous solution or slurry formed from an inorganic base and a compound having in the molecule at least one halogenatable amido or imido nitrogen atom, and (ii) a brominating agent and/or a chlorinating agent; or
B) at least three separate feeds, one of which is a brominating agent and/or a chlorinating agent, and at least two other feeds, at least one of which is selected from (a) and (b); and at least one of which is selected from (c) and (d), wherein
(a) is an aqueous solution or slurry formed from an inorganic base,
(b) is an aqueous solution or slurry formed from an inorganic base and a compound having in the molecule at least one halogenatable amido or imido nitrogen atom,
(c) is a compound having in the molecule at least one halogenatable amido or imido nitrogen atom, and
(d) is an aqueous solution or slurry formed from a compound having in the
molecule at least one halogenatable amido or imido nitrogen atom;
in proportions such that at least one such amido or imido nitrogen atom is substituted by a bromine or chlorine atom, thereby continuously or substantially continuously forming product which precipitates in an aqueous reaction mixture continuously or substantially continuously, during all or substantially all of the time the concurrent feeding is occurring, and such that the pH of the mixture is continuously or substantially continuously maintained in the range of about 5.5 to about 8.5 during all or substantially all of the time the concurrent feeding is occurring.
Another preferred process for the N-halogenation of a compound having at least one halogenatable amido or imido functional group in the molecule is one in which there are in essence two separate feeds to effect the desired reaction. Such process comprises concurrently feeding separate feeds into a reaction zone so that the feeds form, or continue to form, a reaction mixture. These separate feeds are composed of (i) an aqueous solution or slurry formed from an inorganic base and a compound having in the molecule at least one halogenatable amido or imido nitrogen atom, and (ii) a brominating agent and/or chlorinating agent in proportions such that at least one such amido or imido nitrogen atom is substituted by a bromine or chlorine atom and the resultant product precipitates continuously or substantially continuously in an aqueous reaction mixture during all or substantially all of the time the concurrent feeding is occurring, and such that the pH of the mixture is continuously or substantially continuously maintained in the range of about 6.5 to about 8.5.
A particularly preferred group of reactants used in the practice of this invention is comprised of the 5-hydrocarbyl and especially the 5,5-dihydrocarbyl hydantoins. Of these reactants the 5,5-dialkylhydantoins are even more preferred. Accordingly, still another preferred embodiment of this invention is a process for the production of a 1,3-dihalo-5,5-dimethylhydantoin, which process comprises concurrently feeding into contact with each other feed streams of (i) water, inorganic base, and 5,5-dimethyihydantoin, these being fed separately and/or in any combination(s), and (ii) a separate feed of abrominating agent and/or a chlorinating agent, in proportions such that 1,3-dihalo-5,5-dimethylhydantoin is formed in an aqueous reaction mixture in which the pH of such mixture is continuously or substantially continuously maintained in the range of about 6.5 to about 8.5, and where the 1,3dihalo-5,5-dimethylhydantoin precipitates during all or substantially all of the time the concurrent feeding is occurring.
Another preferred process of this invention is a process in which the N-halogenation is conducted on a semi-batch or more preferably on a continuous basis. Such process comprises:
I) concurrently and continuously feeding into a reactor containing an aqueous reaction mixture:
A) separate feeds of (i) an aqueous solution or slurry formed from an inorganic base and a compound having in the molecule at least one halogenatable amido or imido nitrogen atom, and (ii) a brominating agent and/or a chlorinating agent; or
B) at least three separate feeds, one of which is a brominating agent and/or a chlorinating agent, and at least two other feeds, at least one of which is selected from (a) and (b); and at least one of which is selected from (c) and (d), wherein
(a) is an aqueous solution or slurry formed from an inorganic base,
(b) is an aqueous solution or slurry formed from an inorganic base and a compound having in the molecule at least one halogenatable amido or imido nitrogen atom,
(c) is a compound having in the molecule at least one halogenatable amido or imido nitrogen atom, and
(d) is an aqueous solution or slurry formed from a compound having in the molecule at least one halogenatable amido or imido nitrogen atom;
in proportions such that at least one such amido or imido nitrogen atom is substituted by a bromine or chlorine atom and a precipitate of the resultant product precipitates in an aqueous reaction mixture during all or substantially all of the time the concurrent feeding is occurring, and such that the pH of the reaction mixture is continuously or substantially continuously maintained in the range of about 5.5 to about 8.5; and
II) periodically or continuously removing precipitate and a portion of the reaction mixture from the reactor.
When using a brominating agent in any of the above processes, it is possible pursuant to this invention to recover the bromine values produced as bromide in the process. Such an operation can improve the overall process economics. One such embodiment of the invention comprises:
a) concurrently feeding into a reactor (i) water, inorganic base, and a compound having in the molecule at least one halogenatable amido or imido nitrogen atom, these components being fed separately and/or in any combination(s), and (ii) a separate feed of a brominating agent, in proportions such that (iii) at least one such amido or imido nitrogen atom is substituted by a bromine atom, (iv) the product continuously or substantially continuously precipitates in an aqueous reaction mixture in which the pH is continuously or substantially continuously maintained in the range of about 5.5 to about 8.5, and (v) an aqueous solution of co-product inorganic bromide salt is formed;
b) separating precipitate from the aqueous solution; and
c) oxidizing co-product inorganic bromide salt in the solution to form elemental bromine.
Preferably the pH in each of the above embodiments is maintained in the range of about 6.5 to about 8.5. It is particularly preferred to conduct the above processes while maintaining the pH within the range of about 6.8 to about 7.2, especially when the N-halogenatable reactant is a hydantoin.
As noted above, each process of this invention can be conducted in a batch mode, in a semi-batch mode, or in a continuous mode.
Other embodiments and features of the invention will become still further apparent from the ensuing description and appended claims.